first using the figures provided on this website determine the theoretical angle of the sun on the equinox for your latitude using basic trig.
Now on the next several equinoxes Mar Sept measure the actual angle is and you will find a severe discrepancy
2007 21 18:06 23 09:51 that is irreconcilable with a flat earth model.
2008 20 23:59 22 15:44
2009 20 05:45 22 21:18
2010 20 11:28 23 03:09
2011 20 17:16 23 09:04
2012 20 23:09 22 14:49
2013 20 05:04 22 20:44
2014 20 10:51 23 02:29